Messages in this thread | | | Date | Mon, 24 Feb 2020 12:22:06 +0100 | From | Boris Brezillon <> | Subject | Re: [PATCH v3 4/5] i3c: add i3cdev module to expose i3c dev in /dev |
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On Mon, 24 Feb 2020 11:04:50 +0000 Vitor Soares <Vitor.Soares@synopsys.com> wrote:
> Hi Boris, > > From: Boris Brezillon <boris.brezillon@collabora.com> > Date: Fri, Feb 21, 2020 at 22:32:16 > > > On Wed, 19 Feb 2020 01:20:42 +0100 > > Vitor Soares <Vitor.Soares@synopsys.com> wrote: > > > > > +static int i3cdev_detach(struct device *dev, void *dummy) > > > +{ > > > + struct i3cdev_data *i3cdev; > > > + struct i3c_device *i3c; > > > + > > > + if (dev->type == &i3c_masterdev_type) > > > + return 0; > > > + > > > + i3c = dev_to_i3cdev(dev); > > > + > > > + i3cdev = i3cdev_get_drvdata(i3c); > > > + if (!i3cdev) > > > + return 0; > > > + > > > + /* Prevent transfers while cdev removal */ > > > + mutex_lock(&i3cdev->xfer_lock); > > > + cdev_del(&i3cdev->cdev); > > > > When cdev_del() returns there might be opened FDs pointing to your > > i3cdev [1] ... > > Yes, I know. I protected the driver part but I missed the > file->private_data.
Not sure what you mean by protection, but if you meant locking, then it's not enough: you need to refcnt the struct if you want to prevent use-after-free situations.
BTW, I had a closer look at the usbdev implementation, and maybe you should base yours on usb instead of i2c. They seem to register a cdev at module init time, and add a dev_t per device at device registration time. Not sure how they handle the userspace-driver vs kernel-driver concurrency, but maybe returning EACCES (or EBUSY) instead of detaching/attaching the i3cdev everytime a device is bound/unbound would be simpler.
Also, I think Arnd was right, it'd be simpler if i3cdev support was integrated to the core (still left as a option so it can be disabled, but with a dedicated i3cdev field in i3c_device instead hijacking the driver private field).
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